In order to achieve a highly accurate positioning, it is necessary for a positioning apparatus to enhance a vibration isolation characteristic of a positioning-target object. To isolate vibrations from an external portion, the positioning-target object is supported by an extremely weak spring element and driven by a lorentz force. Employing a weak spring element makes it possible to virtually disregard the spring property, and employing the Lorentz force cuts off transmission of a vibration between a stationary member and a movable member and isolates the vibration from an external portion.
For empty-weight supporting means having a spring element, for instance, a mechanical spring, a permanent magnet, or an electromagnet, or the like, may be used. For driving means employing a Lorentz force, a linear motor, or the like, may be used. As a result of the attempt to enhance the vibration isolation characteristic of the positioning-target object, the positioning-target object will have a structure that has virtually no physical contact with an external portion, in some cases, a non-contact structure.
Heat enters or exits by thermal conduction, convection, or radiation. However, in a vacuum atmosphere, entrance or exit of heat by convection does not occur. Furthermore, as mentioned above, as a result of the attempt to enhance the vibration isolation characteristic of the positioning-target object, the positioning-target object has a structure that has virtually no physical contact with an external portion. Therefore, the amount of thermal conduction is very limited.
In other words, when a vibration isolation characteristic of a positioning-target object is to be enhanced in a vacuum atmosphere, since the amount of heat of the positioning-target object is not emitted externally by thermal conduction or convection, the amount of heat is accumulated in the positioning-target object. In such a case, even if the amount of inflowing heat [W] is small, because it is extremely hard for the heat to escape externally, the amount of heat [J] gradually accumulates, and the temperature of the member gradually rises.
Particularly, in a case of an exposure apparatus, the amount of heat, e.g., exposure heat, chuck heat (in a case of using an electrostatic chuck), and so on, flows into a substrate and its accompanying members when exposure is performed. As the amount of heat accumulates, the temperature of the members, such as the substrate, or the like, rises.
In general, a precision instrument dislikes a temperature rise of members. Taking an exposure apparatus as an example, the temperature rise causes various detrimental effects, such as poor exposure accuracy caused by thermal deformation of a substrate subjected to positioning, or poor positioning accuracy caused by a change in a measurement reference resulting from thermal deformation of a top plate supporting the substrate, and so on.
A refrigerant pipe may be provided to the positioning-target object to realize heat recovery using a refrigerant. However, a refrigerant pipe can become a vibration transmission factor that transmits an external vibration to the positioning-target object through the refrigerant pipe, or can become a source of a vibration caused by a refrigerant flowing through the pipe or a force disturbance induction due to deformation of the pipe at the time of driving. Therefore, providing a refrigerant pipe is not preferable from the standpoint of the primary object of a positioning apparatus (vibration isolation of a positioning-target object). Furthermore, if a sensor for measuring a temperature is directly pasted on the positioning-target object, the outgoing line of the sensor deteriorates the vibration characteristic, similar to the refrigerant pipe.
Accordingly, it has been an issue how to prevent the temperature rise of the positioning-target object by recovering the heat flowing to the apparatus in a vacuum atmosphere, while ensuring the vibration characteristic (vibration isolation characteristic), that is, the positioning characteristic.